Implants that are used for insertion into bone, for example titanium screws to be placed into the jaw for attachment of artificial teeth are known per se. The function of such an implant can be hampered by an insufficient bone volume or the presence of bone defects at the site of implantation. An often applied measure to promote bone formation at the implantation site is Guided Bone Regeneration (GBR). In this procedure, the site where bone formation is desired is separated from the surrounding soft tissue by a barrier membrane that inhibits non-osteogenic soft tissue cells from entering the site, thus allowing cells from the bone marrow to fill it with bone. Additionally, an osteoconductive bone filling material can be used to support the membrane.
There are several types of cell-occlusive membranes that are used in the field of guided bone regeneration or tissue regeneration in general. Commercially available cell-occlusive membranes can be grouped according to their origin into xenogenic membrane material derived from individuals of different species and synthetically manufactured membrane material.
Xenogenic material always bears the risk of infection. Most membrane materials are sold in sheets and need to be cut to size by the surgeon, which is time consuming. Further this procedure results in difficulties due to shape matching. An example for a xenogenic material is collagen, which is biodegradable and hydrophilic.
An example for synthetic material is PTFE (Teflon). The PTFE membrane is hydrophobic and therefore does not attach well to biological tissue and often has to be attached using pins or screws. Furthermore the material is not biodegradable and thus has to be removed after the healing process in a second invasive procedure.
Biodegradable materials are known in the art. In WO 01/92584 a matrix material is disclosed which is formed by nucleophilic addition reaction to conjugated unsaturated groups. A pharmaceutically active component is covalently attached to the biomaterial, which will be subsequently released into the body. The biodegradable material degrades under physiological conditions within one month.
WO 00/44808 also discloses a polymeric biomaterial formed by nucleophilic addition reactions to conjugated unsaturated groups. The obtained hydrogels may be used for example as glues or sealants and as scaffolds for tissue engineering and wound healing applications. Also said hydrogels degrade fast under physiological conditions.
U.S. Pat. No. 5,874,500 discloses a crosslinked polymeric composition comprising a first synthetic polymer containing two or more amino groups covalently bound to a second synthetic polymer containing multiple electrophilic groups and a biologically active component. Said composition may be used to effect adhesion between a first surface and a second surface, to effect tissue augmentation, to prevent the formation of surgical adhesion and to coat a surface of a synthetic implant.